Polymerization catalyst and production thereof



United States Patent POLYNIERIZATION CATALYST AND PRODUC- TION THEREOFJohn Paul Hogan and Robert L. Banks, Bartlesville, Okla., assignors toPhillips Petroleum Company, a corporation of Delaware No Drawing.Original application Mar. 26, 1956, Ser. No. 573,877, now Patent No.2,825,721, dated Mar. 4, 1958. Divided and this application Jan. 6,1958, Ser. No. 707,131

13 Claims. (Cl. 252-467) This invention relates to a catalyst for thepolymerization of olefins and an improved method for the preparation ofsuch a catalyst. In one aspect, it relates to the preparation of acatalyst containing hexavalent chromium.

This application is a division of our copending application Serial No.573,877, filed March 26, 1956, now US. Patent No. 2,825,721, which is acontinuation-inpart of our applications Serial No. 333,576, filedJanuary 27, 1953, and Serial No. 476,306 filed December 20, 1954, thelast two mentioned applications now being abandoned.

It is known that propylene and other low-boiling monoalkylethylenes canbe polymerized in the presence of metal halide catalysts to producepolymer products of diiferent viscosities within the lubricating oilrange. Polymer products having improved viscosity characteristics havealso been obtained by polymerizing monoalkylethylenes in the presence ofdissolved aluminum bromide catalyst and catalyst promoter, such ashydrogen bromide, under conditions conducive to maximum growth ofpolymer chains. By this process, propylene polymer prod ucts in 100percent yield, having a viscosity at 210 F. of 15,000 SUS, or higherviscosities which cannot be measured, have been obtained. Moreparticularly, the desired polymer products are obtained by admixingmonoalkylethylenes and aluminum bromide solution in the presence ofhydrogen bromide to produce a polymerization reaction mixture as a firststep, and thereafter, as a second step, adding monoalkylethyleue slowlyto the polymerization reaction mixture. The twostep process producedpolymer products of higher viscosity than were obtainable by processespreviously employed. Prior to this invention, the polymerization ofolefins to tacky and solid polymers had not been catalyzed by a highlyoxidized metal oxide as the essential catalyst ingredient, even thoughmetal oxide catalysts had been used in catalyzing the polymerization ofolefins to liquid polymers, such as propylene dimer and tetramer.

An object of this invention is to prepare a catalyst containinghexavalent chromium. Another object of the invention is to prepare animproved polymerization catalyst. Another object of the invention is toprovide an improved method for the preparation of a polymerizationcatalyst. A furthertobject of the invention is to provide a methodwherein a chromium-oxide-containing catalyst is activated underconditions favorable for the existence of hexavalent chromium in saidcatalyst. Further objects and advantages of the invention will becomeapparent from a consideration of this disclosure.

In accordance with this invention, polymers, including novel tackypolymeric products and/or solid polymers, are obtained by polymerizingpolymerizable olefinic compounds in the presence of chromium oxideassociated with at least one oxide selected from the group consisting ofsilica, alumina, zirconia, and thoria. Solid polymers can be producedfrom monoolefins and from diolefins. Chromium oxide is an essentialcatalytic ingredient for the production of high molecular weight tackyand/or solid polymers according to this invention. This catalystcomprising chromium oxide is highly active in polymerizing certainolefins to these heavy polymers. However, its capacity to polymerizeolefins to maximum yields of tacky and/or solid polymers appears to behighest in connection with l-olefins having a maximum of 8 carbon atomsand no branching nearer the double bond than the 4-position. It doespolymerize olefins other than those mentioned, but the polymers arepreponderantly normally liquid. While the ensuing description dealsprincipally with liquid-phase operation, vapor-phase operation, withouta diluent, or with a diluent in liquid phase (so-called mixed-phaseoperation), is efifective in producing tacky and/ or solid polymer.

Diolefins, e.g., butadiene and isoprene, are among the l-olefinspolymerized to solid polymers over our chromium oxide catalyst. In thecase of conjugated diolefins, a methyl group can be closer to a doublebond than the 4-position. The diolefin must have at least one terminaldouble bond. Conjugated diolefins can have small substituents, e.g., CHC H as close as the 3-position to the terminal double bond.Nonconjugated diolefins exhibit the same characteristics as l-olefins inour process.

The unique polymers according to this invention are characterized by thefact that their unsaturation is preponderantly of the trans-internal orterminal vinyl type. Certain of them are characterized in that theirunsaturation is almost entirely of the terminal vinyl structure.

Throughout the specification, it is to be understood that the term totalpolymer as applied to polymers of propylene, designates all polymerboiling above the monomer (but not including any diluent, of course);the semi-solid polymer constitutes the mixture or residuum remainingafter distilling ofi, or otherwise removing, the light oil boiling belowabout 900 -F.; the tacky polymer is the lower molecular weight portionof the semi-solid polymer, which portion can be extracted therefrom withn-pentane at room temperature; and the solid polymer is the highermolecular weight portion of the semi-solid fraction, which constitutesthe raflinate or insoluble portion leftfrom the extraction withn-pentane or methylisobutylketone (MIBK). Ethylene polymers according tothis invention are composed preponderantly of normally solid material;only small amounts of tacky or liquid polymer are ordinarily producedfrom ethylene. Polymers of l-butene, of l-pentene, and of4-methyl-l-pentene according to this invention are similar to those ofpropylene. It will be readily understood by those skilled in the art,however, that the molecular weight distribution in any given polymerwill depend upon, not only the polymerization conditions, but the natureof the monomer employed. Thus l-hexene, l-heptene and l-octeneordinarily give relatively low yields of normally solid polymer andrelatively high yields of semi-solid, highly viscous, or tacky polymer.However, 4-methyl-l-pentene produces higher yields of solid polymer thandoes l-hexene or l-pentene.

The polymerization of propylene over the catalyst according to thisinvention yields a total polymer product of about 2000 to 50,000 averagemolecular weight. The molecular weight of narrow fractions of thepolypropylene produced by the process of this invention in the presenceof chromium oxide supported on silica, alumina, or silicaalumina rangefrom about 200 to 100,000 or higher. Our polypropylene ordinarilycontains about 10 to 20 Weight percent of material boiling below 900 F.This fraction is an oil having an initial boiling point of about 400 F.The fraction boiling above 900 F. contains both tacky and solid polymer.

The tacky polymer product is useful in the manufacturing of surgical andpressure sensitive tapes, calking and sealing compounds, laminatedpaper, hydraulic fluids, tracing paper, electrical capacitors, surfacecoatings, rubber extenders, etc. Certain fractions of the polymerproducts are particularly useful as lubricating oil and as V.I.improvers and blending materials for lubricating oils. The solidpolymers and copolymers of the invention have utility in applicationswhere solid plastics are used. They can be coated on wire to provideinsulation. They can be extruded to form filaments. They can be moldedto form articles of any desired shape, for example, bottles and othercontainers for liquids. They are particularly desirable in theseapplications on account of their relatively high softening points whichmake them amenable to sterilization with superheated steam withoutdeformation. They can also be formed into pipe or tubing by extrusion.

The catalyst according to this invention can be prepared by preparationmethods knoWn in the art, e.g. direct mixing of solid components,impregnation, etc. In order to obtain optimum activity, it is preferredthat the catalyst mixture comprising chromium oxide and the additionaloxide as hereinbefore specified be heated under elevated temperature andfor a sufficient time to activate,

or increase the activity of, said catalyst for the polymerizationreaction. It is also preferred that the catalyst be heated undernonreducing conditions in an atmosphere such as oxygen, air, nitrogen,carbon dioxide, helium, argon, krypton, or xenon. Reducing gases such ashydrogen or carbon monoxide can be present in said atmosphere where thetime of contact with the catalyst, especially at the highertemperatures, is limited to prevent extensive reductionof the hexavalentchromium; however, the presence of such gases, and of reducing agents ingeneral, is ordinarily not desired. It is ordinarily preferred that theactivation atmosphere be nonreducing. It is further preferred that theatmosphere be positively oxidizing, e.g. air or oxygen. The temperatureand time of activation can vary over wide ranges and are closelyinterrelated (so-called time-temperature effect), longer times beingrequired at lower temperatures and shorter times at higher temperatures.Catalysts prepared by milling solid silica, alumina, zirconia and/orthoria with solid oxide are activatable at lower temperatures than arecatalysts prepared by impregnating silica, alumina, zirconia and/ orthoria with an aqueous solution of a chromium compound. As a practicalmatter, a catalyst prepared by dry mixing is ordinarily activated at atemperature of at least about 350 F. and not substantially greater thanabout 1500 F. A catalyst prepared by impregnation with an aqueoussolution is ordinarily activated at a temperature of at least about 450F. and not substantially greater than 1500 F. Times of activation canrange from about a second at the highest temperatures to 50 hours ormore at the lowest temperatures. The stated numerical values are givenas illustrative of the most practical ranges and are not absolutelimits. By using very short times and higher temperatures, or very longtimes and lower temperatures, catalysts having various degrees ofincreased activation are obtainable.

The chromium oxide catalyst can be prepared by impregnation ofparticulate silica, alumina, or silicaalumina, for example, with asolution of chromium oxide or a compound convertible to chromium oxideby calcination, followed by drying and activation of the composite at atemperature in the range of 450 to 1500 F., preferably 750 to 1500 F.,for a period of 3 to 10 hours or more. Activation is conducted byheating in a stream of gas. It is preferred that the gas contain oxygenand be substantially water-free. Preferably the dew point of theactivation gas should be below 75 F., preferably below F. However, inertgases, such as carbon dioxide and nitrogen, can be used. It is foundthat within this activation range of temperature treatment of thecatalyst, the character of the polymer can be contro ed.

after activation.

When the catalyst is activated at temperatures in the upper part of therange, particularly from 1300 to 1500 F., the polymers obtained frompropylene and heavier olefins have a lower average molecular weight andcontain less tacky and solid polymer, while activation temperatures inthe lower part of the range produce a catalyst which effects an increasein molecular weight of the polymer and the production of largerproportions of heavy tacky and solid polymer. The catalyst can beprepared using, as starting material, chromium trioxide, chromicnitrate, chromic acetate, chromic chloride, chromic sulfate, ammoniumchromate, ammonium dichromate, or other soluble salts of chromium. Thehighest conversions were obtained from the catalyst that contained onlychromium oxides impregnation with chromium trioxide (CrO is preferred,although chromic nitrate can be used with similar results. It isbelieved that the catalyst prepared from the chloride and that preparedfrom the sulfate are at least partially converted to oxide duringactivation. The amount of chromium, as chromium oxide, in the catalystcan range from 0.1 to 10 or more weight percent and is ordinarily aminor component of the catalyst in terms of weight percent. Chromiumcontents as high as 50 weight percent are operative, but amounts above10 weight percent appear to have little added advantage for thepolymerization of ethylene. However, for the polymerization of propyleneand higher boiling olefins, chromium contents as high as 25 or 30percent are often advantageous. A preferred nonchromiurn component orsupport is a silica-alumina composite containing a major proportion ofsilica and a minor proportion of alumina. While the method of preparingthe silica-alumina composite undoubtedly affects the catalyst activityto some extent, it appears that silica-alumina composites prepared byany of the prior art processes for preparing such catalytically activecomposites are operative for the process of this invention.Coprecipitation and impregnation are examples of such processes. Onesupport that has been found particularly effective is a coprecipitatedpercent silica-10 percent alumina support. It is found that steamtreatment of certain commercially available forms of silica-alumina orsilica without appreciable alumina, improves the activity and life ofthe catalyst composite in a polymerization reaction. A silica support oflower surface area and larger pore size is a better support than onehaving extremely higher surface area and small pore size. These factorsare believed to be of importance in the removal of the heavy polymerfrom the surface of the catalyst composite. A chromium oxide-aluminacatalyst ordinarily has about twothirds the activity of a chromiumoxide-silica-alumina catalyst. It is necessary for some of the chromiumto be in the hexavalent state to act as an active promoter or catalystfor the polymerization reaction of this invention. It is preferred touse catalyst in which the amount of hexavalent chromium is at least 0.1percent of the weight of the catalyst composite, at least at the initialcontacting with the hydrocarbon. The hexavalent chromium is determinedby ascertaining the water-soluble chromium present by leaching withwater and determining the dissolved chromium in the leachings by anysuitable analytical method known in the art, e.g. addition of potassiumiodide solution and titration of the liberated iodine with sodiumthiosulfate solution.

The preferred steam activation of certain silica-alumina bases,previously mentioned, is conducted at a temperature of approximately1200 F. for 10 hours utilizing 5 volume percent steam admixed withvolume percent air. In the steam activation treatment, the temperaturecan be varied from 1100 to 1300 F. and the steam content of thesteam-air mixture can range from about 3 to about 10 percent. The timeof treatment can vary from about 4 to about 15 hours. 7

Another suitable base or support for our catalyst .atoms per molecule.

is microspherical silica-alumina containing, for example, 10 to 15weight percent alumina.

The molecular weight of the product can be changed by pretreating thecatalyst base, preferably before addition of the chromium oxide, with afluoride, alone or in aqueous or non-aqueous solution, e.g., aqueous oranhydrous hydrogen fluoride or other organic or inorganic fluoride,especially a volatile fluoride such as ammonium fluoride or ammoniumhydrogen fluoride, and heating, e.g., at from 300 to 1100 F. for from0.5 to 10 hours, to remove residual fluoride. This treatment results ina catalyst which, after addition of the chromium oxide, produces apolymer of increased molecular weight and flexibility. From 0001 to 0.2part by weight of the fluoride per part by weight of oxide treatedproduces the improved results, although these figures do not representabsolute limits.

The terms support or base, as used herein, are not to be narrowlyinterpreted. They are not limited to mere inert components of thecatalyst mass. In fact, the nonchromium components appear to impart tothe catalyst at least part of its activity, and variations in theiridentity and proportions affect the catalyst activity. The support ispreferably utilized in the porous form, e.g., a gel.

Other methods of preparing the catalyst, e.g., coprecipitation, arewithin the scope of the invention.

The temperature to be used in carrying out the polymerization reactioncan vary over a broad range but normally ranges from about 100 to about500 F, preferably 150 to 450 F. The preferred range for propylene andhigher olefins is 150 to 250 F., and that for ethylene is 275 to 375 F.when a fixed bed of catalyst is utilized. When a mobile catalyst isused, the preferred polymerization temperature range is 175 to 350 -F.for ethylene and that for propylene and heavier olefins is about 180 to200 F. At temperatures lower than those in the preferred ranges, therate of catalyst deactivation increases and catalyst-bed plugging mayoccur, and at temperatures higher than those in the preferred ranges,the rate of catalyst deactivation increases and polymer molecular weightdecreases. Our polymerization process is a relatively low-temperatureprocess. The maximum temperature of polymerization appears to be that atwhich reaction, other than polymerization, between the hydrocarbon feed,or some component or components thereof, and the catalyst proceeds atsuch a rate, relative to that of polymerization, that polymerization isnegligible, at least as regards the formation of solid polymer. Thistemperature is in the vicinity of 500 F. Ordinarily, the process isconducted at temperatures up to only about 450 F., and usually not above375 F.

The pressure is preferably high enough to maintain any diluent(subsequently discussed) in the liquid phase and to assure that olefinsnot liquefied under these conditions are dissolved in the liquid phasein sufficient amount. This often, but not invariably, requires apressure of at least 100 to 300 p.s.i., depending on the feed and thetemperature, and a pressure of approximately 500 p.s.i. is to bepreferred. The pressure can be as high as 700 p.s.i. or higher, ifdesired. It can be as low as atmospheric when, for example, the reactionis conducted in the gaseous phase. As a general rule, high pressuresfavor the production of high molecular weight polymers, all otherconditions being constant. The feed rate can range from 0.1 to 20 liquidhourly space velocity with a preferred range of 1 to 6 liquid hourlyspace velocity in a liquid-phase process with fixed-bed catalyst.Hydrocarbon diluents, preferably paraffins and/or cyclopar- :aflins,serve as solvents for the polymer products to aid in the removal of theproduct from the catalyst in the reactor or as diluents. The diluentsinclude aliphatic paraffins having from 3 to 12, preferably 5 to 12,carbon Any hydrocarbon diluent which is relatively inert,nondeleterious, and liquid under the reaction conditions of the processcan be utilized.

such as. Z-methylhexane and triptane, normal octane,

normal nonane, the isononanes, cyclopentane, methylcyclopentane, thedimethylcyclopentanes, and the dimethylcyclohexanes can also be used.Methane and/or ethane can be used, especially where gas-phase contactingis practiced, and for liquid-phasecontacting they can be used inadmixture with the heavier hydrocarbons mentioned. The heavierparaifinic diluents have a higher solvent power for the product polymerthan do the lighter ones. However, the ligher paraffins are quite usefulin our process. Aromatic hydrocarbon diluents are operative,althoughless preferred in many cases, since it appears that they requiremore expensive purification than do nonaromatics.

The polymerization can be effected with a fixed-bed catalyst or with amobile catalyst. A frequently preferred method of conducting thepolymerization reaction cornprises contacting the feed olefin with aslurry of the comminuted chromium oxide catalyst in suspension in thesolvent or diluent. From about 0.01 to 10 weight percent of catalyst,based on weight of diluent, is ordinarily used. The catalyst can bemaintained in suspension by a mechanical agitation device and/or byvirtue of the velocity of the incoming feed or diluent. In this type ofoperation, a large portion of the product polymer remains associatedwith the catalyst, which is withdrawn from the reaction zone, as aslurry. The polymer can be separated from the catalyst by dissolution ina solvent of the type described, usually with the aid of heat andagitation, and the stripped catalyst can be recycled and/or regenerated.The regeneration can be accomplished by oxidizing the residualcarbonaceous deposit with a controlled concentration of oxygen in aninert gas by conventional procedures. However the productivity of ourcatalyst is sufliciently high that it is often economical to discard theused catalyst after a single pass through the reactor. In some cases,especially where a pigment such as carbon black is to be added to thepolymer product, or where high polymer productivity is obtained, thecatalyst need not even be' separated from the polymer.

Used catalyst can be regenerated in auxiliary equipment in the usualmanner. The catalyst is first washed with a hydrocarbon solvent, such aspentane, isooctane, or cyclohexane, at a temperature in the range of 300to 400 F. under sufiicient pressure to maintain the solvent in theliquid phase. Following this, solvent vapor is removed by flushing withinert gas and any remaining solid polymer is removed from the catalystwith dry air diluted with inert gas. The temperature at which the solidpolymer is burned off the catalyst is maintained preferably in the rangeof 900 to 1100 F. Solid polymer is recovered from the solvent used inthe washing step and the polymer-free solvent is reusable in subsequentwashings.

Further, according to this invention, special benefits can be obtainedby utilizing, as feed to the process, a mixture of at least twodifferent olefins. For example, ethylene and propylene can becopolymerized, as can ethylene and l-butene, l-butene and propylene, orpropylene and a pentene, in the presence of a chromium oxidepolymerization catalyst. By using a propylene-ethylene mixturecontaining from 10 to 45 weight percent propylene as a feed component, acopolymer is obtained which has increased flexibility and is readilycapable of being extruded to form a film. Films of this type areunusually resistant to moisture-vapor penetration and are useful aswrappings for foods, drugs, chemicals, and the like. By using, as a feedingredient, a propylene-ethylene mixture containing from 0.5 to 10weight percent propylene, spalling or disintegration of the catalystparticles is decreased. This is an advantage in a fixed-bed orgravitating-bed process where filtration is not needed for catalystremoval. A similar effect is obtained by the use of a propylene-ethylenemixture containing from about 1 to about weight percent ethylene. Thepreferred temperature range for ethylene-propylene copolymerization isfrom 175 to 320 F., more preferably 200 to 280 F.

Many of the copolymers of this invention have a flexibility rating, asdetermined by the falling ball method, of at least 72 inches, even whenproduced in a fixed-bed process. This rating is determined by allowing a90-gram steel ball to fall from a measured height and strike a moldeddisc of the copolymer two inches in diameter and one-eighth inch thick.The ball falls along a mechanical guide, and the height from which theball drops is measured. The minimum height required to shatter themolded disc is taken as a rating of flexibility or susceptibility toshattering. The maximum height measurable according to this method andapparatus is 72 inches. Thus, many of the copolymers of this inventionare not shattered by the falling ball within the limits of measurementof the method. In contrast, so-called brittle polymers can be shatteredby the ball when it falls from a much smaller height, such as no morethan 6 to 10 inches.

In addition, diolefins can be copolymerized with 1- monoolefins of theclass herein defined. Thuse ethylene and 1,3-butadiene have beencopolymerized, according to .this invention, in a 9:1 Weight ratio inthe presence of a chromium oxide-silica-alumina (2.5% Cr) catalyst at270 F. to obtain a copolymer having a molecular weight of 33,690.

The polymer and copolymer films prepared according to this inventionhave a moisture penetration rating not greater than 1 gram per milthickness per 100 square inches per 24 hours. The method ofdetermination of moisture transmission or penetration is referred to incertain of the subsequent examples. The films are also characterized byhaving transverse tear strengths of at least 170,and often at least 185,grams per mil of thickness, as determined by a method subsequentlydescribed herein.

Films extruded from solid, flexible, high copolymers prepared by thecopolymerization of ethylene with propylene over a chromiumoxide-silica-alumina catalyst according to this invention have, inaddition to very low moisture-vapor permeability, good tensile strengthand tear strength. They are superior in moisture-vapor permeability tofilms prepared from presently available commercial polyethylenesproduced by other processes. They are particularly desirable for filmpackaging materialsfor meats, cheese, fresh vegetables, dried eggs,milk, etc., and for coating paper to be used as packaging material.Films ranging in thickness from inch to 0.001 inch or less can beprepared from the copolymers of this invention.

Films prepared by blending commercial polyethylene With solid ethylenepolymers prepared over a chromium oxidesilicaaalumina catalyst have lowmoisture-vapor permeability. Films prepared from ethylene-propylenecopolymers, as herein described, have properties as good or better thanthose prepared from blends of the two types of ethylene polymers and, inaddition, there are certain advantages in the process steps for theproduction of the copolymer films. Ethylene-propylene copolymers arereadily prepared and used as such for extrusion into films withoutfurther processing.

Many of the ethylene-propylene copolymers of this invention are flexiblematerials which generally have a melt index less than 25, preferablybetween 0.01 and 1.0. (Melt index, as determined by ASTM Method D 1238-52T, is the rate of extrusion of a thermoplastic material through Janorifice of .a specified length and diameter,

under prescribed conditions of temperature and pressure.)

The following specific examples present data which illustrate andclarify the invention but should not be so interpreted as to restrict orlimit the invention unnecessarily.

SPECIFIC EXAMPLES Example I.-Polymerization of olefins over chromiumoxide-silicw-alum ina Individual monoolefins and diolefins werepolymerized in flow-type runs over a fixed bed of 3 percent chromium asoxide in a chromium oxide-silica-alumina catalyst (prepared byimpregnation with CrO solution, activation above 700 F. in dry air) atabout 600 pounds per square inch at a temperature of about 190 F. and aliquid hourly space velocity of 2, the feed containing 20 mol percentreactant and mol percent isobutane. Most runs were for 4 to 6 hours. Theresults of the conversions and the qualitative nature of the polymersare given in Table I.

TABLE I Average Monomer Conver- Type of Polymer, etc.

510]), percent Normal l-olefins:

Ethylene Solid, slightly waxy. Reactor plugged in 2 hrs. Propylene-.. 91Tacky, semi-solid. l-Butene 77 Tacky, elastic semisolid. l-Pentene 82Tackier than polypropylene;

semi-solid. l-Hexene 40-56 Veryfitacky, transparent semiso 1 l-Octene 58Tacky, contained about 4 wt. percent solids including wax (possiblydimer or trimer). l-Dodocene 16 (Run at 260 F.) liquid. Normal2-olefins:

2-Butene 5 Liquid (dimer and trimer). Z-Pentene 5 Do. Z-Hexene. 11 Do.Z-Octene... 1 Wax ()probably dimer and trimer. Branched l-0lefi us:

Isobutylene 87 Liquid (dimer and trimer). 2-Methyl-1-butene. 6 Do.3-Methyl-1-butene 15 Do. 4-Methyl-1-pentene 80 semisolid.4-Viny1cycl0hexene 6 Liquid. Branched 2-olefins: 2- 12 Do.

methyl-Z-butene. Cyclic Olefins: Oyclo- 5 Do.

hexene. Diolefins:

Butadiene. 55 Solid. Isoprene 34 D0. Aryl Olefins: Styren 0 ExampleII.-Efiect of temperature on propylene conversion I Runs were made withchromium oxide-silica-aiumina (weight ratio SiO :A1 'O =9:l) catalystcontaining 3 percent chromium as chromium oxide (prepared as in Example1), operating at 600 pounds per square inch, a liquid hourly spacevelocity of 2, and a feed consisting of 11 mol percent propylene, 14 molpercent propane, and 74 mol percent isopentane. The data oh- 1 sroz=A-1203 ratio, a :1 by weight.

tained are given in Table II and indicate an optimum temperature rangeof 150 to 250 F.

, Hydrocarbon diluent was varied in runs made at 180 to 190 F., 600pounds per inch, two liquid hour-1y space velocity of feed containingpropylene, propane and other diluent. The results are given in TableIII. An improvement in conversion was obtained as the molecular weightof the feed diluent was increased from propane to isobntane to pentaneor isopentane. No further improvement was obtained in shortruns withisooctane as diluent. However, in longer runs, isooctane showedimprovement over the other diluents, as shown in Table IV. I

. TABLE III Feed Composition, Percent CsH Conv.,

M01 Percent Hrs. Solvent Tested Solvent C3135 03115 2 3 4 5 Propane-- 2s75 82 s2 86 Isobutane... 88 12 90 92 87 n-Pentane 75 12 13 91 95 96Isopentana. 75 12 13 93 95 97 97 Isooctane 66 17 17 84 92 96 98 TABLEIV.--OPERATION .efiilfigag F., 600 P.S.I.G., 2 LHSV OF [Containing 9 molpercent C3H6, 12 mol percent Crib, 79 mol percent solvent] SolventIsopentane Isooctane The catalyst had the same composition as that inExample II and was prepared in the same manner, i.e.,

impregnation and activation as previously described.

Example IV.Suspended catalyst Shaker-autoclave tests were made to studybatch operation and to determine the effects of varying the feed-Percent CaHs Conversion, Hrs.

to-catalyst ratio in this type of operation. The catalyst was 14/28 meshsilica-alumina promoted with 3 percent by weight of chromium as chromiumoxide and activated at 930 F. (preparation as previously described). Thefeed stock was a blend of 20 mol percent technical grade propylene and80 mol percent technical grade isobntane. The catalyst was suspended inthe liquid charge in the shaker-autoclave for six hours at a temperatureof 190 F. The results of these tests are shown in Table V. For aconstant reaction time of 6 hours, the total propylene conversiondecreased from 98 percent with a 4:1 feed-.to-catalyst weight ratio to18 percent with a 50:1 ratio. However, calculations showed (see Table V)that the grams of propylene converted per gram of catalyst increasedfrom 0.54 with a 4:1 feed-tocatalyst' ratio to 1.41 with a 10:1 ratio,and thereafter remained relatively constant.

3 Si02:A120;,, 9 :1 by weight.

has v raorynaNa CONVERSION mi GRAM' or CATALYST IN AUTOCLAVE TESTS v r il liinhour tests at 190 F. with 20 niolglercent 0:115, mol percent iC He ee Grams CaH Converted Per Gram of Catalyst Feed-to Catalyst WeightRatio Percent CaHr Converted Exam ple V.C'hr0m'z'um oxide content of thecatalyst To determine the eliect of chromium oxide content of thecatalyst up'on activity of the catalyst and nature of the product,catalysts were prepared by impregnating a commercial steam-agedsilica-alumina support with aqueous chromium nitrate or trioxidesolutions over a wide range of concentrations. The results of propylenepolymerization tests with these catalysts are shown in Table VI. Thesupport contained weight percent silica and 10 weight percent alumina.The catalyst was activated by heating for several hours at 900 to 1000F. in anhydrous air.

TABLE VI.-VARIATION OF GHROMIUM OXIDE CONTENT OF CATALYST Commercialsteam-aged silica-alumina, 14/28 mesh; promoted with various amounts ofchromium oxide.. Runs made at to F., 600 p.s.i.g., and a 2 LHSV' of 12mol percent propylene, 13 mol percent prop aneg, 75 mol percentisopentane feed.

Percent C313 Conv., Hrs.

Chromium Content of 1 Nature of Polymer: Catalyst, Wt. Percent 73 83 9488 Sirupy semi-solid.

66 87 94 97 Semi-solid, tacky.

From the results shown in Table VI, it appears that the preferablechromium oxide content of the silicaalumina support was in the range ofone to three weight percent, expressed as chromium, under the conditionsinvestigated. The catalysts of higher chromium oxide content producedwhat appeared to be slightly more viscous polymer, but the efiect wassmall considering the range covered.

TABLE VII Five-hour runs with ethylene were made at 308 to 313 F., 400p.s.i.g., 4.6 to 5.2 LHSV of about 3 weight per-- Table VIII presentsthe results obtained with supports of varying silica-alumina ratio andsource, and from supports other than silica-alumina.

Each catalyst was prepared by impregnating the. 14/28 mesh supportwithan 0.8 molar aqueoussolution of chromium nitrate, drying, andactivating for five hours at 930 F. in dry air. The finished catalystcontained 7 TABLE VIII.SURVEY OF CATALYST SUPPORTS Chromiumoxide-promoted catalysts were prepared from the supports shown.Polymerization tests at 180 F., 600 p.s.i.g., and 2 LHSV of 12 molpercent propylene,

13 mol percent propane, 75 mol percent isopentane feed.

Percent OBI-I Oonv. Catalyst Support 2hr. 3 hr. 4hr. 5hr.

Silica gel 77 85 85 98% silica, 2% alumina 69 76 33 90% silica, %alumina(extruded pellets) 93 95 97 90% silica, 10% alumina (beads) 73 90 93 j64% silica, 46% alumina (Filtrol) 79 77 67 5% silica, 95% alumina 62 7269 Alumina gel 45 I 36 HI -treated alumina g 53 39 35 Bauxi 62' 57 60Brucite (magnesium oxide) 0, Activated carbon 0 86% SiO210% ZrO;4% A110:89' 95 94 Chrome-bead SiO2Al2O3 (0.4 wt. percent 1 Cr) 90 V 86 v I 56 1High molecular weight tacky and solid polymerwas producedin all runs inwhich propylene was converted.

It is seen from Table VIII that, although conversion of propylene wasobtained over the entire range of silicaalumina ratio, the catalysts ofhighest activity were prepared from coprecipitated 9 0 silica-l0 aluminasupports. The 54 silica-46 alumina support was an acid-activatedhalloysite clay.

The commercial pellets and commercial bead supports were of the sameapparent chemical composition (90 water by addition of 2 liters of 28percent aqueous animonia, mixing the filtered, undried gel with 9.5 ml.of 47 percent aqueous hydrofluoric acid in 200 ml. of water, stirringfor 2 hours,- drying the mixture at 215 F. for 24 hours, calcining at750 to 800 F. for 20 hours, forming the solid into pellets by use of ahydrogenated vegetable oil as a binder, and burning out the binder atabout 1000 F.

The two supports containing neither silica nor alumina gave noconversion of propylene. A catalyst prepared with commercialsilica-zirconia-alumina cracking catalyst as support gave goodconversion. The commercial chrome-bead silica-alumina cracking catalyst,already containing 0.5 percent chromium oxide, produced high molecularweight polymer from propylene with no further addition of chromium oxidebut the activity declined relatively rapidly.

Example VII.-Metal oxide components A survey of the available metaloxides as possible catalyst components was made and the results of thesurvey are presented in Table IX. In each case, commercialcoprecipitated steam-aged 90 silica-10 alumina. was impregnated with anaqueous solution of the compound shown in the table, and the catalystwas dried and then activated at 930 F. in dry air. In most cases, theactivated catalyst contained about three to four weight percent of themetal as oxide. The activated catalyst was tested for propylenepolymerization under the conditions given in Table IX.

TABLE IX.-SURVEY OF METAL OXIDE PROMOTERS Commercial 90 silica-10alumina, 14/28 mesh, promoted with the compounds listed. Polymerizationtests at 160 F., 600 p.s.i.g., and 2 LHSV of 25 percent pro-' pylene,percent propane feed, 5-hour runs.

1 Times other than 5 hr. are shown in parentheses.

percent silica, 10 percent alumina), but the pelleted support, which wasprepared by coprecipitation and steam aging, appeared to provide a moresatisfactory catalyst. On account of the difierences in methods of 65preparation of these two supports, the commercial pellets have lowersurface area and larger pore size than the beads and have a greater'number of so-called macropores per unit weight or volume. These factorsare believed to be of importance in the removal of the heavy 70 polymerfrom the chromium oxide-silica-alumina catalyst surface.

ThefHF-treated alumina in Table VIII was prepared by precipitatingalumina gel from 3640 grams of alu-' It is seen from Table IX that onlychromium oxide promoted the formation of high molecular weight polymer.A number of other metal compounds acted as promoters for the formationof liquid polymer, as can be seen by comparing the conversion obtainedin eachrun with that obtained with the unpromoted silica-alu mina base,shown at the bottom of the table.

Example VIII .-Survey of chromium compounds as catalyst componentsCatalysts were prepared from various soluble chromium compounds byimpregnation of commercial steamaged silica-lO alumina with an aqueoussolution of minum nitrate nonahydrate in solution in 28 liters of 7i;vthe compound, followed by drying and activatingat 930 team 13 F. in dryair. Each catalyst was then tested in a propylene polymerization run asdescribed in Table X.

TABLE X Commercial steam-aged 90 silica-10 alumina, 14/28 mesh,impregnated with 3 to 4 weight percent chromium as compounds listed.Polymerization tests at 160 F., 600 p.s.i.g., and 2 LHSV of 25 molpercent propylene, 75 mol percent propane feed.

14 in methylisobutylketone (MIBK) at 200" F. and a solvent to polymerratio of 40 ml. to one gram. The analyses reported in Tables Xi and X11were on polymer samples collected in the solvent-removal flash chamberduring the run.

As shown in Table XI, the activity of the catalyst increased as thecatalyst activation temperature was increased over the range of 750 to1500 F. The amount of heavy ends in the polymer, as indicated by theamount Percent H Conv. Polymers Impregnating Solution Probable ComponentDescription 2 Hrs. 5 Hrs.

82 86 semisolid, tacky. r 75 84 Do. 011313.611: r0 66 49 DO. C12(04)3.5Ha0 Crz(SO4)3CIzO3CIOa S6 50 Sirupy, tacky. H2 Reduction of CrOq,Cat Orzo: 25 (4 h 1)7 Liquid.

As shown in Table X, all of the catalysts prepared from the variouschromium compounds produced high molecular weight polymer, but thehighest conversions were obtained from the catalysts that contained onlychromium oxides after activation, i.e., those prepared from chromiumnitrate and chromium trioxide. Whether the catalysts prepared from thechloride and sulfate produced high polymer only as a result of partialconversion of chloride or sulfate to oxides during activation is notknown but seems likely.

Treatment of chromium oxide catalyst with hydrogen for four hours at 920F. to reduce hexavalent chrotmium to the trivalent state gave a catalystwhich was almost completely inactive for formation of high polymer. Thisindicates that hexavalent chromium is essential. Analyses have indicatedthat a major portion of the chromium oxide present on the catalystsactivated at 930 F. in air was hexavalent. (Note Tables XI and XII.)

Example IX.--Variation of catalyst activation temperature The effects ofcatalyst activation temperature on catalyst activity and character ofpolymer were determined over a temperature range of 750 to 1500 F. Thecatalysts were tested in six-hour propylene polymerization runs at theconditions described in Table Xi.

TABLE XI Catalyst, 14 to 28 mesh commercial steam-aged 9O silica-10alumina impregnated with chromium oxide, tested in six-hourpolymerization runs at 190 F., 600 psi, and 2 LHSV of 12 mol percentpropylene, 13 percent propane and 75 percent isopentane feed.

1 Does not include heavy material which remained on the unfiushedcatalyst.

The data in columns 3, 4, and 5 present the weight percent of chromiumon the catalyst, the amount of hexavalent chromium, and the fraction ofthe chromium that is hexavalent. The amount of hexavalent chromium wasdetermined on the basis of water-soluble chromium.

The heavy ends were determined by filtering and weighing the portion ofpolymers which were insoluble of MIBK insoluble at 200 F., was affectedby the activation temperature, and apparently the molecular weight ofthe polymer decreased at the higher activation temperatures.

The ratio of hexavalent chromium to total chromium on the catalystdecreased as the activation temperature was increased.

Several catalysts were prepared by impregnation off commercialmicrospheroidal (99 wt. percent finer than: 100 mesh) silica-alumina(about 13.3 wt. percent aIumina, remainder essentially silica) with anaqueous: solution of chromium trioxide. The catalysts were tin-- idizedin dry air during activation. Polymerization tests; were carried out ina batch-type stirred reactor at 4501 p.s.i.g. and 270 F. usingcyclohexane as solvent. Ap proximately 300 grams of solvent and from0.45 to 1.0 gram of catalyst were charged to the reactor. After' heatingthe reactor contents to reaction temperature, the; reactor was pressuredwith ethylene to within 50 p.s.i.. of operating pressure within thefirst five minutes, and,, after the operating pressure of 450 p.s.i.g.was attained,, ethylene was fed at the rate required to maintain that;pressure. The duration of each run was three hours. The results, whichare presented in Table XI-A, show; that, as a practical matter, theminimum activation tem-- perature for the catalyst tested lies between400 and? 450 F. when the polymerization is carried out under: theconditions of these runs. If thedata for the activations at 450, 555,650, 700, and 750 F. are plotted on rectangular nonlogarithmiccoordinates and if more: weight is arbitrarily assigned to the point at650 F. than to that at 555 F., the minimum activation tem peratureappears to lie between 430 and 440 F. The minimum activation temperaturewould be lower if relatively long activation times were used. From apractical point of view, the minimum activation temperature can beconsidered to be about 450 F. This activation temperature applies onlyto catalysts prepared by a wet method such as impregnation. This pointis subsequently discussed in more detail.

TABLE Xl'A.-ACTIVATION TEMPERATURE FOR. CATALYST PREPARED BYIMPREGNA'IION Catalyst Activation Catalyst Testing.

Per- Per- Reaction; Temperature, Time, cent cent Productiv- Rate,

F. Hours Tgtal Cr+ ity, #1# #/#/Hr-.

5 2. 38 1. 68 v535 17$ 5 2. 30 1. 46 607 202 5 2. 22 1. 18 277 92 52.36 1. 24 185 62 5 2. 14 0.97 .113 35 20 2. 99 1.73 99 3b 20 3. l3 1.96 6. 6 2. 2 20 3.13 2.30 O 0 shaking in a flask. Portions of thismixture were further 19 treated as described in Table XI-B, and theresulting catalysts were tested for polymerization activity in a Aftercooling to room temperature, 195 grams 1 6 greatest activity. Apparentlythis level of moisture content is not reached in a reasonable time attemperatures much below 450 F. On the other hand, when a dry method ofpreparation is used, for example, mixing of solid CrO with calcinedsilica-alumina, the moisture content need not be limiting, and theminimum temperature appears to be that at which the CrO "has sufiicientmobility to become distributed on the surface of the silica-alumina.minimum temperature appears to be a little below 350 F., although 350 F.could be considered as a minimum from a practical point of view.

PREPARATION BY DRY MIXING Catalyst Preparation Catalyst Testing PercentPercent Percent Method of Mixing CrO; with Silica-alumina Total Gr+ Losson Yield, Cr Ignition 1 Catalyst Fluidization 2 at 80 F. for two hours2. 5-3.0 2. 73 (0.1 Fluidization at 400 F. for two hours. 2. 5-3. 1. 563. 6 Ball-milled in Dry N; at 80 F. for 15 hours 2. -3.0 2. 64 2. 83 0 4Ball-milled hours, followed by fiuldization at 400 F. for two hours 2.5-3. 0 2. 74 13 8 Ball-milled l5 hours, followed by fluidization at 050F. for five hours 2. 96 1. 49 1. 91 376. Calciued Silica-alumina with noCrO 1. 28 0. 1 Ball-milled 15 hours, followed by fluid at 350 F. for twohours 4. 2

1 Heated at 1760 F. in air for 10 hours. Figures not corrected for Crloss. 1 All fiuidization was done with dry air. 8 0.5 gram catalyst usedin the polymerization test.

batch-type, stirred reactor at 450 p.s.i.g. and 270 F. Example X.Efiectof aging of catalyst with dry air and About 300 grams of cyclohexane and10 grams of catalyst were charged to the reactor, and, after heating thereactor contents to reaction temperature, the reactor was pressured toreaction pressure with ethylene within five minutes. The run durationwas two hours. The results, which are presented in Table XI-B, indicatethat optimum activity is obtained by heating. The loss-on ignition dataindicate that moisture was not excessive in any catalyst tested and,consequently, that it was not limiting.

Upon examination of the data of Tables XI-A and XIB, it will be notedthat the impregnated catalyst activation series appears to show that thecatalyst should be treated at a temperature of at least around 450 F. tohave commercially desirable activity, while in the mixing series acatalyst having appreciable activity was prepared by heating at 350 F.The reason for this difference is believed to reside in the differencein the catalyst preparation methods. When a wet method of preparation,such as impregnation by aqueous solution,

with wet air To study the eifects of prolonged treatment of the catalystwith dry air (dew point below 0 F.) and with wet air at elevatedtemperatures, such as would be encountered in repeated regenerations,the catalysts were aged 88 hours at 1100 F. and 1300 F. with dry air andat 1100 F. with air saturated with water vapor at F. At the end of theaging period with the wet air, which contained about 6.5 percent watervapor, the catalyst was swept with dry air for five hours at 1100 F.Results of the polymerization test on these catalysts and similar dataon unaged catalysts are shown in Table XII.

TABLE XII Catalyst, 14/28 mesh commercial steam-aged 90 silica-l0alumina impregnated with chromium oxide, tested in six-hourpolymerization runs at F., 600 p.s.i.g., and 2 LHSV of 12 mol percentpropylene, 13 percent propane and 75 percent is'opentane feed.

1 Does not include heavy material which remained on the unflushedcatalyst.

1 Wet air contained about 6.5 percent water vapor.

Catalyst was flushed with dry air for five hours at 1100 F. after thewet air treatment.

is. used, the water content of the catalyst must be re- As shown inTable XII, treatment with dry air; for 88 llQQitQ. a, certain. level.for. the catalyst. to possess its 75 hours @1100? resulted in a catalystwhich had slightly For microspheroidal silica-alumina, this higheractivity and produced a lighter weight polymer did not afii'ect thecatalyst activity or polymer distribution. The ratio of hexavalent tototal chromium on the catalyst was not affected at 1100 F., butdecreased slightly at 1300 F. by the prolonged treatment.

Treatment with air containing about 6.5 weight percent water vapor for88 hours at 1100 F. decreased the activity of the catalyst considerablyand, as compared with the run at 1100 F. for 88 hours, doubled thefraction of polymer insoluble in MIBK at 200 F. This catalyst, whichcontained less than 0.1 percent hexavalent chromium, was a bright-greencolor as compared to a of spelling, i.e., crumbling or shelling off ofthe outer layer of the pellets, whereas the catalyst of higher aluminacontent remained in good physical condition. The steam-aged 90silicaalumina support resisted physical disintegration in contrast tothe untreated support having the same composition.

Example XIL-Bflects of variation of operating tem perature Furtherstudies were made on the effects of operating temperature, and longertests and more accurate evalua tions of the polymer were obtained.Results and operating conditions of these tests are shown in Table XIV.The polymer analyses were on samples which included gray-green thattreated h ry at l1 0 the polymer flushed from the reactor at the end ofthe All of t datt} Presented 1n the Prevlous mp runs. Comparisons ofpolymers were based on the were obtalned 1 8 14 28 mesh Catalyst pquantity of light and heavy ends. The light ends were except asQtherwlse deSCflbed, T data Presented 111 determined by vacuumdistillation and are reported as the Succeedlllg 671311119168 wereObtalfled y contattmg thfi weight percent polymer boiling below 850 F.at one f f With 5/ 32 inch p of copl'eclpltated atmosphere pressure. Theheavy ends were determined 511163-10 'alllmlna lmPregnated With9111011111191 0X1de by filtering and weighing the portion of polymerswhich q q e). except where spemfically mdlcated were insoluble inmethylisobutylketone (MIBK) at 200 otherwlse. 1 F. and a solvent topolymer ratio of 40 ml. of one gram.

Example XL-Catalyst supports: variation of silica- TABLE XIV alummaOperation at 600 p.s.i.g. and 2 LHSV of 7 mol percent Catalyst supportsof 90-10, 50-50, and 10-90 silicapropylene, 9 percentpropane and 84percent isopentane alumina compositions were prepared by pilling amixture feed over chromium oxide-90 silica-10 alumina pelleted ofsilicic acid and precipitated alumina and calcining at catalystactivated at 1300 F. in dry air.

Polymerization Tests Polymer Analysis Physical Percent Propylene Oonv.,Hrs. Wt. MIBK Condition Operating Percent insoluble of Used Temp, F. w850 at:200 Catalyst 5 10 20 F. F., Wt. Percent 190 94 88 4s 20 s 10 10.2Spalled 220 95 92 72 52 44 1a 7.3 Good. 245 91 79 2s 27 5.1 Good (20hrs.).

1000 F. The catalyst bases were impregnated with 08- The maximumconversion and longest cycle length at molar chromium trioxide solutionand activated at 1300 high conversion were obtained at 220 F; Themolecu- F, in dry air. Results and operating conditions of the 5 larweight of the polymer decreased, as shown by the polymerization tests onthese catalysts along with data increase in 850 F. polymer and decreasein MIBK on catalysts prepared using commercial steam-aged 90 insolublepolymer, as the temperature was increased silica-10 alumina base areshown in Table XIII. from 190 to 245 F. About 25 percent of the catalystTABLE XIII used in the run at 190 F. was spalled or crumbled. d t al st5324mm enets 55 Most of this catalyst dlsintegratlon occurred in the topchmmmm oxlde'pmmote ca 1 P 1 (inlet) portion of the catalyst bed. Thecatalysts used were prepared from the.support 8 0 ymenza on in the runsat the higher temperatures remained in good tests at 220 F., 600p.s.1.g. and 2 LHSV of 7 mol percent Physical condition. Propylene, 9Percent pmpaneand 84 Percent lsopentane Although higher conversion wasobtained and less physical damage to the catalyst occurred at 220 F.,polymer containing greater amounts of tacky and solid Pl 1 u T t-P t 7 oCatalyst pp 0 t g z n q geen ghysilqal materials was produced at 190 F.operating temperature. 7 55%,23 Example XIII.--Efiects ,of variation ofpropylene con- Porcent Percent Catalyst rentration Silica Alumina 2 5 1016 The effects of propylene concentration in the feed 10 90 62 a9. 29 26Good. upon conversion, polymer composition, and catalyst spall- 72 42GoOding were studied with feeds containing 4, 7, and 12.5 90 10 as 91 6517 Spelled. 90 1 10 94 95 92 84 Good. percent propylene. Results ofthese runs are shown in V p Table XV. Commercial, steam-aged. I 7 TABLEXV As showninTable X111, increasing the silica content of Operation at220 F., 600 p.s.i.g., and 2 LHSV of the base from 10 to 90 percentincreased the initial catafeed containing propylene, propane andisopentane over lyst activity. After the 15-hour tests, the catalystprepelleted steam-aged 90 silica10 alumina-chromium oxld pared, from 90silica-.10 alumina support showed signs catalyst activated at 1300 F. indry air.

Polymerization TestsPereent Polymer Analysis M Propylene Conv., Hrs. F d01 l reent Physical Propylene Wt. MIBK Condition 5 20 30 40 PercentInsoluble 01 Used 850 200 Catalyst 95 88' 54 28 16 19 5. 8 Good. 7 95 9272 52 44 16 7. 3 Good. 12.5 94 86 a 69 40 24 14 6. 2 Spalled.

Optimum conversion was obtained with the feed containing 7 mol percentpropylene. The feed with higher propylene concentrations producedslightly heavier polymer. Catalyst spalling occurred when 12.5 percentpropylene feed was used.

The polymer production for the 40-hour run using 12.5 percentpropylene'feed was 3.6 pounds of polymer per pound of catalyst ascompared to 2.2 for the 7 percent propylene feed.

The polymer produced from alpha-olefins over a chromium oxide-containingcatalyst has a wide molecular weight range. The total polymer can beseparated into three fractions, a liquid fraction, a tacky fraction, anda solid fraction containing material at the upper end of the molecularweight range. The separation may be carried out by a number ofdifl'erent methods, and the relative amount and the characteristics ofthe various fractions will depend somewhat on the method offractionation used. Two methods of separation are currently used: 1) Thetotal polymer is fractionated under vacu- 11m to produce an overheadfraction having an end point, correlated to atmospheric pressure, of 850to 900 F. The kettle material is then extracted with MIBK at atemperature somewhat. above room temperature yielding as extract thetacky polymer and as rafiinate the solid polymer. (2) The total polymeris subjected to extraction with pentane at room temperature, the solidfraction being insoluble. The pentane-soluble material is thenextracted, usually twice, with MIBK at room temperature yielding anextract of normally liquid oil and a raflinate of tacky polymer. Method(1) produces considerably less oil and more tacky polymer than method(2). The oil produced by method (2) probably contains in solution someof the lower molecular weight tacky polymer. However, in the case ofethylene polymerization, only very small amounts of nonsolid polymer areproduced.

'The weight average molecular weight of this tacky propylene polymerlies in the range of 500 to 5,000. The solid polymer fraction isinsoluble in pentane at room temperature. The solid material has amelting point in the range of 240 to 300 F., a density in the range of0.90 to 0.95, an intrinsic viscosity in the range of 0.2 to 1.0, and aweight average molecular weight in the range of approximately 5,000 to20,000.

The polyethylene of the invention is principally a solid polymer havinga freezing point in the range of 240 to 260 F., a density in the rangeof 0.92 to 0.99, ordinarily 0.95 to 0.97, an intrinsic viscosity in therange of 02m 10, and a weight average molecular weight in theapproximaterange of 5,000 to 250,000. The melting point is determined from acooling curve of temperature vs; time; actually, this is a freezingpoint, though generally termed melting point in the art.

The. molecular weights mentioned herein are-weight average molecularweights and were calculated according to the equation 130 C. This typeof molecular weight determination is described by Kemp and Peters, Ind.Eng. Chem. 35, 1108 (1943), and by Dienes and Klem, J. Applied Phys, 17,458 (June 1946).

In addition to the properties discussed hereinbefore, our polyethylenesprepared by the use of a slurried cata lyst, as described herein, have atensile strength of the order of 4000 p.s.i. and higher, an elongationat break of from 10 to percent (crosshead speed, 20 inches per minute),an impact strength from about 1.5 to about 3, a Shore hardness of fromabout to about 70, a stiffness of at least about 140,000 p.s.i., abrittleness temperature below about -150 F. and usually below about180F. and a softening temperature of at least 250 F. and usually 260 F.or higher. They have a low permeability to gases and vapors and can berolled, drawn,or blown to form film which is useful for the preservationof foods'and other perishable goods. They can also be coated on wire asinsulation.

We have further found that highly crystalline (above 80 percentcrystallinity) normally solid polymers can be obtained by extractingpolymers produced according to this invention, including the fixed-bedand mobilecatalyst embodiments thereof, with common organic solventssuch as isopentane, normal pentane, chloroform, benzene, methyl isobutylketone, cyclohexane,

. undissolved portion.

normal heptane and similar, relatively low-boiling solvents attemperatures from about 50 F. up to the normal boiling point of thesolvent and recovering the The crystalline fraction of such a' polymeris insoluble whereas the amorphous fraction is soluble in the solventunder such conditions. Crystalline polymers of propylene, of l-butene,of l-pentene, and of 4-methyl-1-pentene can thus be obtained. Those ofpropylenes are characterized by selective absorption of infra-redradiation atcertain wave lengths of "about 7.7, 7.9- to 8.0, 8.5 to 8.6,9.1, 9.6-, 10.0 to 10.1, 10.3, 10.6 to 10:7, 11.1 and 11.9 microns.These polymers,

and crystalline polymers of propylene and hig'her-boih" ing olefins ingeneral are described in more detail in our copending application SerialNo. 558,530, filed January 11, 1956. These polymers are alsocharacterized by the constant recurrence, in their molecules, ofdefinite and certain atomic groupings in which the sub- -stituent groups(eg. methyl and other side groups or chains) are oriented according to adefinite pattern.

Example XIV Q and a liquid hourly space velocity of 4.5. The feed to Vthe reactor, which contained a fixed bed ofthe catalyst, consisted of 99weight percent 2,2,4-trimethyl-pentane and 1, weight percent of theolefin mixture. The fol;- lowing results were obtained for thatfraction'of the 21 total copolymer which was insoluble in2,2,4-trimethylpentane at room temperature:

The films in this example were prepared by utilizing an extrusionapparatus manufactured by the Modern TABLE XVI.-ETHYLENE-PROPYLENE COPOLYMERIZATION Run Number 10 13 1 4 6 Weight ratio, G lli/C 116" 90/1085/15 80/20 75/25 60/40. Percent Total olefin conversion 9R 9 93 93. 84.Weight Percent converted olefin to:

Solid polymer 7 64 as 50 42, i-gsoluble polymer... R 22 22 an Catalystdeposits 18 14 10.-.. l1- 8. Solid Polymer: Impact strength 0.660 0.8430. 1.216.-.. 1.89.

(Izod), ft.lbs. Tensile strength of injection Molded 2,587 2,415 2,1711,910 1,957.

sam le, lb sq. in. Shore D ardness 5 50 51 55. Molecular Weight25,550.-. 25,210 24,500 25,300.-. 26,300. Rating (flexibility) brittle.can be bent but cracks can be bent 180 same as 1-- can be bent 180 manywhen bent 180. several times. times without breaking or cracking.

The foregoing data show that, when the propylene content of the olefinfeed was less than about 15 weight percent under the stated conditions,the resulting copolymer was brittle, and that when 40 percent propylenewas present in the olefin feed, a polymer having much greaterflexibility was obtained. It is evident that the conversion efficiencydecreases with increasing propylene content. When the propylene contentof the feed is above 45 percent, based on total olefin in the feed, theefficiency is still lower than the values shown in Table XXVI and theproduct more nearly resembles polypropylene.

Example XV containing one percent by weight olefins in the isooctane.'Ihe ethylene-propylene copolymer obtained had a melting point of 236F., a density of 0.930, inherent viscosity of 0.987, and a melt index ofapproximately 12. A film was prepared from this polymer by extruding iton a Modern Plastics 1 /2 inch extruder.

Plastics Machinery Corporation, 15 Union Street, Lod-i, New Jersey. Themachine effects film formation on the principle of feeding a groundpolymer at a temperature above its softening point through an annulardie and injecting air into the extruded annular film to form an inflatedfilm. The inflated film can be recovered without further treatment orcan be passed between a pair of rollers. It is, however, within thescope of the invention to utilize other known means for producing films.

Example XVI Five runs were made in which ethylene was polymerized overchromium oxide-silica-alumina catalyst prepared as in Example XIV,containing 4.5 to 5.0 weight percent chromium oxide. Operatingconditions were 250 F., 450 p.s.i., 4.5 LHSV, 2 weight percent totalolefin in feed, and 10-hour operation utilizing a suspended catalyst(stirred) in a continuous flow reactor. The concentration of propylenein the olefin feed was varied from zero to weight percent. The data areshown in tabular form below. The percentage of fines is that weightpercent of the total catalyst, after the runs, which was finer than theoriginal catalyst.

TABLE XVIII For comparative purposes, a film was prepared from acommercial poly- Wt. Percent Felling Oat. ethylene (melting point up to228 F., density 0.914 to Egg /1 22%,} fi 11%? 0.918), and two. filmswere prepared from blends of Fines the commercial polyethylene with asolid polymer of ethylene alone obtained by polymerization of ethylene82 249 0960 500 24 4 6 over a chromium oxide-silica-alumina catalyst andhav- 3;} $3 813g 31% 3g 8; ing a melting point of 244 F., a density of0.961, and 2 79 2 0.937 30,900 72 0 5 an inherent viscosity of 0.585.Tensile strength, elongao 79 236 0'932 ZGOOO 72 1 4 tion, tear strength,and moisture-vapor transmission were obtained on each of the four films.Results were as From the above data, it is evident that, under the confollows: ditions of these runs, when the propylene concentration TABLEXVII Tensile Elongation, Tear Moisture-Vapor Strength, p.s.i. PercentStrength Transmis- Type of Film sion ---G./mil/ 100 sq. in./ T.D. M.D.T.D. M.D. I.D. M.D. 24 hours Ethylene/propylene copolymer a 1,245 1,05020 6.2 197 169 0.53 1 Commercial polyethylene 2,060 l, 950 528 464 163166 1.11

20/80 blend ethylene polymer/commercial polyethylene 1,387 1,568 265 152195 160 0.67 30/70 blend ethylene polymer/commercial polyethylene 1,6881,497 214 186 135 0.59

1 TD. represents transverse direction; M.D. represents direction ofextrusion or machine direction.

2 AS TM D 1004-491. Calculation in grams/mil thickness.

8 ASTM D 697-421 (Method B). A modification of this methodwas used witha Payne permeability cup being employed instead of a standard cup. Inthe Payne permeability cup, the area exposed is 10 sq. cm. as comparedto 30 sq. cm. for the standard cup. Runs were made at 100 F. instead ofat room temperature.

The foregoing data show that the process of this invention produces afilm which is superior to commercial polyethylene as regardsmoisture-vapor transmission and tear strength. I

in the feed was 10 percent or higher, the polymer properties differedmarkedly from those of the homopolymer, and the differences increasedwith increasing concentration. Furthermore, it is evident that theaddition of the 23 first 5 to 10 percent of propylene to the olefin feedmarkedly reduced catalyst spalling, as measured by the amount of fines,and increased the conversion; further addition of propylene resulted inlittle, if any, further decrease in catalyst spalling.

Example XVII Several runs were made in which small amounts of ethylenewere added to a propylene feed to a polymerization step according tothis invention. Comparative runs were made in which no ethylene wasadded to the propylene feed. The food had the following composition inWeight percent:

Total olefins .a 4.5 Propane 5 2,2,4-trimethylpentane 9 l The feed wascontacted with a fixed bed of catalyst containing 2.5 weight percentchromium as chromium oxide. The catalyst was prepared as in thepreceding examples and activated in anhydrous air at 950 F.

The polymerization was conducted at a pressure of 600 psi. and a liquidhourly space velocity of 2. The duration of each run was 12 hours. Thefollowing data The data show that spalling is more marked at the lowerpolymerization temperatures and that the spalling is reduced by thepresence of small amounts of ethylene, which also tend to increase theolefin conversion per pass.

' Example XVIII This example illustrates the production, according tothis invention, of flexible polyethylene in a continuous flow system.

The catalyst had a maximum particle size of about 20 mesh. It wasprepared by the use of a crushed, commercial silica-alumina crackingcatalyst which contained 90 percent silica and 10 percent alumina in theform of a coprecipitated gel. The crushed, coprecipitated gel wasimmersed in an aqueous solution of chromium trioxide, and the resultingsolid composite was separated from the liquid and drained. It was thendried by heating at 500 F. in a stream of air having F. dew point andwas finally activated by heating in a stream of air (0 F. dew point) at925 to 960 F. for hours. The resulting. catalyst contained 2.34 weightpercent total chromium as chromium oxide. The hexavalent chromiumcontent was 2.00 weight percent.

The catalyst was suspended in a stream of 2,2,4-trimethylpentane as thediluent and passed into a reactor provided with a stirrer. Ethylene waspassed into the reactor at the same time. An effluent was withdrawn fromthe reactor and contained suspended catalyst, solvent and polymer, aswell as small amounts of mire-- acted ethylene. Additional diluent(2,2,4-trimethylpentane) was added to the effluent, and the resultingmixture was passed to a tank having a vent valve through which unreactedgas was vented. The remaining material was heated to dissolve thepolymer and the resultingmixture was passed through a filter to removethe 24 catalyst. The polymer was recovered from the resu1t-. ing liquidby vaporization of the diluent. Table XX shows the reaction conditionsin two separate runs.

Table XXI shows the properties of the product polyethylene.

, TABLE XXI Run Number I II Volatile matter, wt. percent 0. 04 0.14Melting point, F 248 Density. 0. 966 Softening point, 9 F 262 261Molecular weight 44, 000 47,000 Melt index 0.640 0.356 Tensile, p.s.i.:

Injection-molded sample 4, S 5, 308 Compression-molded sample-.. 3, 2604,196 Elongation, percent: 7

Injection-molded sample 22 19 Compression-molded sample. 12 19 Hardness,Shore D 68-70 68-70 Flex. Temp., F +76 +72 Impact, IZOD. 2. 46 2. 31Heat distortion, F. 163 165 Tensile, p.s.i.:

T.D MVT-gm./100 sq. in./24 hr-.

curve.- The temperature corresponding to a plateau in the cooling curvewas taken as the melting point.

The density was determined at 23:1 C. by immersion in .a solvent havinga density equal to that of the polymer, a Westphal balance beingutilized.

The softening point was determined by the use of a Goodrich plastometeras described by Karrer, Davies and Dieterich, Industrial and EngineeringChemistry, Analytical Edition, 2, 96-99 1930). On the plasticity curve(temperature v. softness) obtained according to the published method,the point at which the tangent to the curve had a slope of 60 wasdetermined and the corresponding temperature was read on the temperatureaxis.

The molecular weight was determined as scribed herein.

The melt index was determined by ASTM Method D-1238-52T.- I

The tensile strength and the elongation were determined by ASTM. MethodD-638-52T for the injectionmolded samples and by ASTM D 412-51T for thecompression-molded samples. The Shore hardness was determined by AST MMethod D-676-49T.

The flex temperature was determined by ASTM Method D1043-5 1.

The impact strength was determined Method D-256-47T.

previously dew ASTM The heat distortion was determined by ASTM MethodD-648-45T.

The film properties were determined by methods previously cited herein.

As a general rule, the use of a stirred reactor and a suspended catalystpermits practical operation at lower temperatures and produces arelatively flexible polyethylene having a high molecular weight, whereasthe use of a fixed or stationary catalyst mass often requires a highertemperature and produces a relatively brittle polyethylene having arelatively low molecular weight. Within the disclosed ranges, however,higher temperatures favor production of brittle polyethylene havingrelatively low molecular weight, and lower temperatures favor productionof relatively flexible polyethylene having relatively high molecularweight. High catalyst activation temperatures favor lower molecularweights, and vice versa. Thus, even when a stirred reactor and asuspended catalyst are utilized, relatively brittle polyethylene (m. wt.10,000-20,000) can be produced at temperatures in the range 350 to 450F. and/or by using a catalyst which has been activated by heating in airat a temperature in the range 1100 to 1500" F. The same type ofcontacting technique conducted at a temperature in the range 200 to 350F. with a catalyst activated at 9001100 F. produces a relativelyflexible polyethylene having a molecular weight in the range 20,000 to200,000. Also, above 1 weight percent, low chromium content in thecatalyst favors the formation of low molecular weight, brittle polymer,and high chromium content favors the formation of high molecular weightflexible polymer. High concentrations of monomer in the reaction zonefavor production of high molecular weight polymer. With these factors inview, those skilled in the art can select the proper conditions for theproduction of polyethylene having the desired properties in anyparticular case.

Example XIX Several materials were tested as supports for chromium TABLEXXII [Four-hour fixed-bed polymerization tests at 330 F. maximumtemperature, 450 p.s.i.g., and 6 LHSV, 3.0 wt. percent ethylene, 1.2%ethane and 95.3% isooctane (recycled) feed over 100 ml. of pelletedcatalyst. Catalysts prepared by impregnation 01 supports with 0.76 MCrOa solution and activation 26 oxide in runs wherein a solution ofethylene in 2,2,4-trimethylpentane was contacted with a fixed bed ofcatalyst under the conditions shown in the following tables.

The supports for the chromium oxide catalyst were prepared by thefollowing method: (1) the major component was slurried with water in aball mill for approximately 12 hours; (2) the resulting slurry was thenmilled together with the nitrate or the oxide of the minor components;(3) the resulting slurry was then milled with ammonium hydroxide; (4)the resulting mixture was dried at 180 to 250 F.; (5) the dried materialwas calcined at about 900-1000 F.; (6) the calcined material was againmilled with water; (7) the resulting mixture was dried; (8) the driedmaterial was calcined; (9) the resulting oxide material was formed intocylindrical pills; and(10) the pills were further calcined. 1n the caseof the catalyst in which the major component of the support was silica,steps 5, 8, 9 and 10 of the foregoing procedure were omitted, andfollowing step 7, the dried powder was extruded; calcined, and steamaged, as previously described herein, in connection with the discussionof the silica-alumina composites. The alumina used in the preparation ofthe catalyst was a commercial alumina trihydrate. The silica was acommercial silica hydrogel. The zirconia was a commercial high surfacezirconia oxide.

Oxide mixtures wherein each of copper oxide, calcium oxide, zinc oxide,manganese trioxide, cobalt trioxide, iron trioxide, tin dioxide,titanium dioxide, magnesium oxide, vanadium pentoxide, antimonytrioxide, molyb denum trioxide, tungsten trioxide, and nickel oxide, wasused as the sole support for the chromium oxide effected substantiallyno ethylene conversion under the conditions of the runs.

In the following tables, values in parentheses are estimated values.

at 950 F. with thy aim] Catalyst Percent Ethylene Charged Going to-Isooctane Insoluble Polymer Polymer- Properties lTzatlon Su ort es s ppAverage Isooctane Unac- Wt. Bulk Ethylene Unre- Isooctane Insolublecounted Molec- I Dcn- Melt- Falling Surface Per- Den- Conv., actedSoluble Polymer for ular sity at lng Ball, Composition Area, cent sity,Percent Ethylene Polymer (Recov- (Cata- Weight 20 C. Point, Inchesmfl/g. Cr g./cc. ered lyst De- F.

posits) 90 S10 -10 Al O 350 2. 5 0. 63 97 3.3 4. 2 65. 6 26. 9 12,6000.955 243 6 103 7, sirxjufni "in: 2. 53 0. 49 93 6. 8 2. 7 55. 0 35. 517, 000 0.952 243 6 100% 1 03 2. 53 0.66 40.1 1. 7 28. 9 29. 3 15, 3000.960 245 131M 90% SiOz10% CuO. 5. 7 0.41 96 4. 4 3. 3 71. 5 20.8 14,200 0. 955 244 6 90% S10210% 02.0. 5. 2 0. 52 91 9. 0 2. 9 63. 7 24. 416, 400 0.951 243 6 90 03-10% Zn 5. 3 (0. 40) 96 2. 8 3. 3 72. 5 20.414, 400 0. 9531 244 BIM 90% SiO210% Mg0 3. 9 0. 49 91 9. 5 2. 9 65. 222. 4 22, 200 0. 959 246 12 90% Sim-10% SrO 5. 8 0. 40 96 3. 6 3. 7 83.39. 4 14, 500 0. 952 245 90% Sl0 10% Ba 5. 2 (0.40) 93 a r 6.8 2. 9 70. 819. 5 12, 100 0. 952 243 BIM 90% Sim-10% B203. 3.8 0. 46 15. 3 3. 1 60.021. 6 11, 100 0.961 246 BIM SiOz10% Th0; 4. 4 0.42 79 21. 1 1. 5 56. 520. 9 13, 700 0. 960 244 90% S1O210% WO= 3. 5 0. 55 95 5.0 4.0 66. 724.3 14,300 0. 958 245 BIM 90 Slog-10% MNzO3 5. 2 0. 40 97 3.1 2. 7 74.6 19. 6 12, 900 0. 966 244 BIM 90% S10z10% C0203 5. 0 9. 45 98 2. 3 1. 748. 5 47. 5 16, 500 0.965 245 BIM 90% SlOz-10% F8203 4. 8 0. 40 95 4. 82. 5 71. 0 21.7 14, 600 0.956 246 BIM 90% mica-10% CuO 2. 2 r 0.82 1090. 5 0. 2 4. 8 4. 5 20, 600 90% Alz0310 2. 6 0. 68 58 t '42. 0 1. 3 23.7 33.0 16, 600 0. 962 246 6 90% A12o310% ZnO 1. 6 0.85 74 26. 2 1. 5 37.9 34. 4 11, 300 0. 965 246 6 90% Alma-10% Mg 2.1 0. 89 74 26.2 2. 5 37.9 33.4 14,400 0. 958 245 6 90 Alma-10% SrO 2. 2 0.98 75 25. 4 3. 3 38. 133. 2 18, 100 0.954 245 6 90% A12O310% Ba 2. 2 0.89 79 a 21. 2 2. 5 40.6 35.7 14,700 0. 958 246 BIL/I 90% AlzOa-10% B203" 1. 9 0. 87 82 18.3 1. 7 35. 0 45.0 21, 400 0. 963 247 12 90% AlzOa-10%MoOa 2. 0 0. 90 4951. 0 1. 2 13. 8 34. 0 12, 600 0. 967 247 BIM 90% AlzO310% W'O3 2.0 0.86 '74 25. 8 2. 3 47. 3 24. 6 21, 700 246 12 90% A1zOal0% M11203 2. 50.78 64 35. 9 1. 7 29. 4 33.0 13,900 0. 963 245 BIM 90% Alz0310 1. 90.93 82 18. 5 3. 3 49. 8 28. 4 22,400 0.966 248 18 90% AlzOa-10% FezOa2. 6 0. 76 56 43. 7 1. 3 26.2 28. 8 14, 900 0. 964 .246 BIM 1 Reactorflushed at end of run with isooetane for one hour at 370 Fl 4 BIM-brokein mold. B Reactor outlet plugged at 4 hours on stream. Reactor notflushed.

TABLE XXIII [Fou -hour fixed-bed polymerization tests at 330 F. maximumtemperatures, 450 p.s.i.g., and 6 LHSV, 3.0 wt. percent ethylene,0.81.2% ethane and r 95.896.2% isooetane (recycled) feed over 100 ml. ofpelleted catalyst. Catalyst prepared by impregnation oi supports with0.76M CrOs solution and activation at 950 F. with dry aha] CatalystPercent Ethylene Charged Going to- Isooctane Insoluble Polymer Polymer-Properties ization Support lests Average Isooctane Unac- Wt. BulkEthylene Unre- Isooctane Insoluble counted Molec- Den- Melt-r FallingSurface Per- Den- Conv., acted Soluble Polymer for ular sity at ingBall, Composition Area, cent sity, Percent Ethylene Polymer (Recov-(Cata- Weight 20 C. Point, Inches mfi/g. Cr g./cc. cred), lyst De- F.

posits) 90% SiO110% A1100 (350) 2. 5 0.60 96 4. 2 3.1 65. 2 27. 5 16,000 0. 953 246 6 100% S101 725 3.0 0. 55 Z 79 21.2 0. 8 39. 6 38. 4 23,000 5 0.980 248 18 2. 5 0. 70 63 37. 5 1. 7 28. 8 32. 15, 900 0.963 2466 21 0.8 1. 75 83 17.0 1. 7 52. 1 29. 2 15, 400 0. 964 249 6 314 4. 6 0.41 91 9. 1 2. 3 73.3 15. 3 16,100 0.960 246 6 255 3.8 0.50 99 1. 4 2. 364. 4 31. 9 14, 200 0.959 247 BIM 484 2. 0 0.67 91 9. 4 2. 9 53. 3 34. 415, 400 0. 961 249 BIM 226 3. 3 0.56 78 21. 9 3. 2 43. 6 31. 3 11,8000.963 247 BIM 33 4. 3 0. 4O 3 41 58. 8 1. O 31. 2 9.0 14, 000 0.959 248BIM 339 3. 6 0.41 96 4. 5 2. 7 58. 7 34. 1- 19, 000 0.955 247 12 276 4.2 0. 48 89 10. 8 2. 1 66.0 21. 1 15, 600 0. 959 246 6 156 1. 9 0. 87 2476. 2 0. 6 6. 7 16. 5 15, 200 249 195 1. 8 0.87 83 17. 1 1.0 41. 3 40. 615, 800 0. 965 247 6 155 2.4 0.85 70 30.0 1.7 37.0 31. 3 14,900 0.959240 121 1. 6 0.90 75 25. 5 1. 9 54.0 18. 6 15, 200 0.965 248 BIM 156 2.4 1.00 86 14.0 2.1 46. 2 37. 7 16, 700 O. 960 246 175 2.0 0.87 4 26 73.6 4. 8 4. 8 21. 6 0 175 2. 2 0. 90 83 17. 4 0.8 38. 8 43.0 18, 000 0.972247 12 907. Alfie-10% C004 162 1.8 0. 82 61 38. 9 1.1 30. 2 29. 8 1 1000.962 246 6 Platinum Reforming Catalyst (0.4 Wt. percent Pt, 0.25 wt.percent 1*, 0.25 wt. percent CI, remainder A1200 gel) 193 4. 3 0. 53 4753. 2 1.0 12. 5 33 3 9, 300 0 969 248 12 1 Calculated from absorptioncapacity of catalyst.

Catalyst was overheated (475 F.) while in contact With isooctane duringstart-up. 3 Catalyst had low surface area.

4 Two-hour run. Most of the converted ethylene remained on the catalyst.

6 Contained some catalyst.

TABLE XXIV [Fixed-bed polymerization tests at 330 F. maximumtemperature, 450 p.s.i.g., and 0 LHSV, 3.0 wt. percent ethylene l3%ethane and 94-96% isooctane (reotycod) feted over 100 ml. of pelletedcatalyst. Catalyst prepared by impregnation of support with 0.76 M 01-01solution and activation at 950 F. wit ry a Catalyst Isooctane InsolublePolymer Polymerization Percent Ethylene Charged Going to- TestProperties Support Average Isooctane Unac- Wt. Bulk Length Ethyl- Ume-Iso- Insoluble. counted Molec- Den- Melt- Fall- Per- Denof ene actedoctane Polymer for ular sity ing ing Surface cent sity, Test, Conv.,Ethyl- Soluble (Recov- (Catalyst Weight at Point, Ball, CompositionArea, Cr g./cc. Hours Percent ene Polymer cred) Deposit) 20 0. F. Inches90% Zion-10% OuO 1'6. 950' 247 BIM 90% Z1O210% S1200 0 0.0 1. 2 7 00.0 1. 2 s 5 0.0 2. 4 10 12 0.4 2. 4 20 0 0.0 1. 2 s 0 0.5 1. 2 7 00%moi-10% BaO s 0.0 1. '4 5s 0.003 240 0 2 0.0 1. 2 5 1a 0.7 1. 4 10 0.074247 BIM 5 0.7 1. 4 15 0 0.0 1. 4 21 0.000 244 BIM 4 0.0 1.78 2 11 0 0.01.05 2 5 0 0.0 1.02 4 7 7 1.1 .1. 77 2 12 10 0.5 1.04 4 as 02.0 0.0 17.320.1 0,000 0.070 245 BIM s 0.7 1. s0 4 17 10 0.0 1.00 4 17 83.5 0.4 0.07.1 0,400 0.070 244 BIM 00% Z1O0'1O% c001- 14 0.7 1.82 4 20 80.0 0.5 0.00.0 12,100 0.005 242 IBIM 100%2402 10 0.5 1.05 4 24 70.0 0.4 11.3 12.3 00.008 2 100% 210. 0.0 1.00 4 05.0 0.4 28.3 10.0 10,000 0.000 248 BIM 0071 010410 2.4001- 074 3.0 0.50 4 00 4.8 3.0 03.0 27.5 14,100 0.053 24500%14120.-10% e101- 203 2.5 0.70 4 07 2.0 1.0 70.4 22.1 ,0 0.051 243 BIMActivated Carbon 530 0.0 0.38 4 04 00.0 2.0 10.5 40.2 0,000 0. 057 240BIM 1 Contained 13% silica and 5% alumina as impurities.

TABLE xxv [Fixed-bedpolymerization tests at 330 F. maximum temperature,450 p.s.1.g., and 6 LHSV, 3.0 wt. percent ethylene, 3% ethane, and 94.2isooctane (riecyzlgdveierll over 100 ml. of pelleted catalyst. Catalystprepared by impregnation of support with 0.76 M CrO; solution andactivation with dry 2. a 50 Catalyst Polymerization Percent EthyleneCharged Going to- Isooctane Insoluble Polymer Test Properties SupportAverage Isoootane Unac- Wt. Bulk Length Ethyl- Unre- Iso- Insolublecounted Molec- Den- Melt- Fall- Per- Denof ene acted octane Polymer forular sity ing ing Surface cent sity, Test, Conv., Ethyl- Soluble (Recov-(Catalyst Weight at Point, Ball, Composition Are/a, Cr g./cc. HoursPercent ene Polymer cred) Deposit) 0. F. Inches 2. 5 0. 61 4 91 8. 6 3.5 66. 4 21. 5 13, 300 0. 953 247 O. 8 1. 75 4 83 17. 0 1. 7 52. 1 29. 215, 400 0. 964 249 6 0. 6 2. 29 2 6 0. 6 2. 4 34 65. 9 0. 6 19. 8 13. 77, 400 0. 963 245 BIM 70 0. 6 2. 40 4 27 72. 8 1. 2 8. 8 17. 2 12, 2000. 958 245 BIM 71 0. 6 2. 24 4 16 50 0.5 2. 37 4 25 75. 4 O. 2 4. 0 20.4 I 8, 100 0. 969 249 60 O. 6 2. 02 4 19 81. 2 0. 4 2. 1 l6. 3 8, 100 0.981 248 52 0. 4 2. 4 28 72. 1 0. 2 4. 2 23. 5 8, 200 0. 971 247 BIM 0. 52. 01 4 22 78. 1 0. 8 15. 0 6. 1 9,000 0. 973 248 64 O. 8 1.95 4 60 40.0 l. 2 33. 4 25. 4 10, 200 0. 967 249 BIM 67 0. 8 l. 87 4 64 36. 2 0. 630. 8 32. 4 12, 200 0. 966 248 36 O. 7 2. 06 4 4 74 0. 7 2. 34 4 83 36.8 1. 9 40. 8 20. 5 19, 700 0. 965 248 6 54 O. 7 2. O9 2 11 63 0. 0 2. 062 9 56 O. 6 2. 19 4 63 37. 3 0. 6 35. 6 26. 5 19, 800 0. 965 249 12 840. 7 1. 88 4 32 68. 0 O. 4 17. 3 14. 3 9, 800 0. 967 246 BIM 74 O. 6 2.22 4 58 42. 3 O. 4 30. 4 26. 9 22, 200 0. 959 251 90% ThOz-10% CeOz -l63 0. 6 2. 06 4 41 58. 8 O. 8 23. 7 16. 7 17, 700 0. 965 250 6 Theforegoing data show that silica, alumina, thoria TABLE XXVI and zirconiaare particularly desirable as supports for a Cat. Mol Wt. Izod chromiumoxldie catalyst according 9 ifi 1 fi i Reaction Pres- Gone. in Reactionfrom Melt Impact W111 be recognized y those 5k1 11ed 111 art 3 sure,p.s.i.g. .Solvent, R e, Inherent Index x term support, as used herein,is not limited to inactive 35 Pemnt a/s/ vlscoslty bar materials.Indeed, the foregoing data show that there are oxides which, when mixedwith chromium oxide, do a 0. 39 lo 34, 300 2. 8 0. 9 not form an activecatalyst for the purposes of this 1n- 23 33 39, 000 L 4 3 vention, andthat others, notably silica, alumina, zirconia, g-

iig 288 8- 3 3-3 and thoria, contribute or enhance catalytic activity. 1320 461500 0: 46 j 5 -It will also be noted that the activity of acatalyst can 8- 8g 13.383 8- i? 5-; be varied by the use of additionaloxides in admixture with the silica, alumina, zirconia and/orthoria. Itwill be further noted that a given auxiliary oxide in the supportincreases the activity in the presence of certain of the main supportcomponents and does not in the presence of others. Thus, copper oxide,zinc oxide, strontium oxide, tungsten oxide, manganese trioxide, cobalttrioxide and iron trioxide increased the activity of the catalyst inwhich silica was the sole support. Zinc oxide, magnesium oxide,strontium oxide, barium oxide, boron oxide, tungsten oxide, manganesetn'oxide and cobalt trioxide increased the activity of the alumina-basecatalyst. Barium oxide increased the activity of the zirconia-basecatalyst, and none of the additional oxide supports tested together withthoria produced any increase in the activity of the catalyst. From theforegoing data, those skilled in the art can select catalysts having thedesired activity for a desired application. Strontium oxide confersspecial properties on the catalyst, as more fully set forth in ourcopending application Serial No. 433,804, filed June 1, 1954, now US.Patent No. 2,846,425.

Example XX Effects of reaction pressure on reaction rate and on certainpolymer properties in the polymerization of ethylone according to ourprocess are shown in Table XXVI. The data were obtained in two-hour runsin a one-liter, batch-type, stirred reactor at 285 F. Purifiedcyclohexane was utilized as a diluent. The catalyst contained 2.5 Weightper cent chromium as oxide deposited on a commercial microspheroidalsilica-alumina and had been activated by heating in dry air (dew pointbelow 0 F.) at 950 F. for five hours. The silicazalumina weight ratio inthe catalyst was approximately 8:1.

The above reaction rates are in terms of grams of polymer produced pergram of catalyst per hour.

The data show that reaction rate increased with pressure up to- 450p.s.i.g. Above this pressure, the reaction rate data were erratic,probablybecause of the low cata-' lyst concentrations utilized. Thecatalyst concentrations at the higher pressures were maintained low inthis particular group of runs in order to facilitate the removal of theliberated heat, which was relatively high at the higher pressures. Thedata also illustrate the .fact that at a constant temperature and in thepresence of a particular catalyst, increased pressure results inincreased molecular weight.

The density and the melting point of the polyethylenes weresubstantially unaffected by pressure change within the range shown inTable XXXI.

From the foregoing, it will be seen that pressures as high as 1000p.s.i. can be satisfactorily used in our process. Pressures of from 700up to as high as 2000 p.s.i. or higher can be used if desired. However,as a general rule, pressures above 1000 p.s.i. are not essential for theobtainment of satisfactory results.

Water, oxygen, carbon monoxide, and most compounds of sulfur, of oxygen,of nitrogen, and of halogens act as poisons for the catalysts of thisinvention. Therefore the concentration of these materials in the feedshould not exceed 1000 parts per million and preferably should notexceed parts per million. More preferably, they should be entirelyexcluded. Water can be removed by lowering the dew point of the feedgas, for example, to 0 F. or lower, by refrigeration or by contact witha dehydrating agent, such as silica. gel. Oxygen 31 can be removed byadsorption or by reaction with a metal such as copper. Carbon monoxidecan be removed by absorption or selective oxidation. The diluent can bepurified by hydrogenation or fractionation. The above removal methodsare well known in the art.

Catalyst regeneration gas or activation gas should be non-reducing and,preferably, free from sulfur and halogen as well as from nitrogencompounds. From 1 to 25 weight percent oxygen can be present in theregeneration gas, and up to 100 percent in the activation gas. Compoundswhich form carbonaceous deposits should be absent.

As will be evident to those skilled in the art, many variations andmodifications can be practiced within the scope of the disclosure andclaims to this invention.

We claim:

1. A process for the preparation of an improved catalyst, which processcomprises depositing chromium oxide on a support component selected fromthe group consisting of silica, alumina, zirconia, and thoria, heatingthe resulting composite at an elevated temperature, under substantiallyanhydrous conditions, and for a sufiicient time to impart, to theresulting mixture, increased catalytic activity for promoting theformation of normally solid polymers of olefins, the resulting catalystcontaining at least part of the chromium in the hexavalent state.

2. In a process for the activation of a catalyst comprising a supportcomponent selected from the group consisting of s lica, alumina,zirconia and thoria and chromium oxide supported thereon by heating atan elevated temperature for a sufiicient time to impart solid polymerforming activity to said catalyst and leave at least part of thechromium in the hexavalent state, the improvement which comprisesconducting the heating under substantially anhydrous conditions.

3. In a process for the activation of a catalyst comprising a supportcomponent selected from the group consisting of silica, alumina,zirconia and thoria and chromium oxide supported thereon by heating atan elevated temperature for a sufiicient time to impart solid polymerforming activity to said catalyst and leave at least part of thechromium in the hexavalent state, the improvement which comprisesconducting the heating under substantially anhydrous conditions in anonreduc- 7 ing atmosphere having a dew point below 75 F.

4. In a process for the activation of a catalyst comprising a supportcomponent selected from the group consisting of silica, alumina,zirconia and thoria and chromium oxidesupported thereon by heating at anelevated temperature for a suflicient time to impart solid polymerforming activity to said catalyst and leave at least 'part of thechromium in the hexavalent state, the improvement which comprisesconducting the heating under substantially anhydrous conditions in anoxygencontaining atmosphere having a dew point below F.

5. In a process for the activation of a catalyst comprising a supportcomponent selected from the group consisting of silica, alumina,zirconia and thoria and chromium oxide supported thereon by heating atan elevated temperature for a sufiicient time to impart solid 32 polymerforming activity to said catalyst and leave at least part of thechromium in the hexavalent state, the improvement which comprisesconducting the heating in air having a dew point below 0 F.

6. A process for manufacturing a chromium oxidecontaining supportedpolymerization catalyst which comprises impregnating at least one memberof the group consisting of alumina, silica, zirconia, and thoria with anaqueous solution of chromium compound convertible to oxide upon heatingso as to deposit an amount of chromium on said member in the range of0.1 to 10 weight percent of the resulting composite, drying the same andcalcining said composite in dry air at a'temperature in the range of 750to 15007 F. so as to convert said compound to chromium oxide in which atleast a portion of the chromium is hexavalent.

7. The process of claim 6 in which the impregnating solution is asolution of CrO 8. A process for manufacturing a polymerization catalystwhich comprises impregnating asiIica-aIumina gel in which the silica isa major ingredient with an aqueous solution of a chromium compoundconvertible to the oxide upon heating so as to deposit at least 0.1weight percent of chromium on said gel, drying the resulting impregnatedgel and calcining the dried gel in dry air at a temperature in the rangeof 750to 1500 F. so as to leave a substantial portion of the chromium inhexavalent form.

9. The process of claim 8 in which the calcination is effected at atemperature in the range of 1300 to 1500 F.

solution is a solution of chromium nitrate.

11. The process of claim 8 in which the impregnating solution is asolution of CrO 12. A process for manufacturing a polymerizationcatalyst which comprisesimpregnating a. silica-alumina gel in which thesilica isa major ingredient with an aqueous solution of a chromiumcompound selected from the group consisting of chromium trioxide andchromic nitrate to deposit from 0.1 to 10 weight percent, based on thetotal weight of finished catalyst, of. chromium on saidgel, drying the,resulting impregnated gel, and calcining the dry gel, in air having adew point below F., at a temperature in the range 750 to 15.00 F. for aperiod of time in the range 1 second at the highest temperatures in saidrange to 50 hours at the lowest temperatures in said range, to leave atleast 0.1 weight percent, based on total catalyst, of chromium inthehexavalent state I p 13. A process according to claim 12 wherein the airhas a dew point of less than 0 F. and said calcining is conducted for aperiod in the range 3 to 10 hours.

Hull May 28, 1 946- FOREIGN PATENTS 751,859 Great Britain July 4, 195610. The. process of claim 8 in which the. impregnating

1. A PROCESS FOR THE PREPARATION OF AN IMPROVED CATALYST, WHICH PROCESSCOMPRISES DEPOSITING CHROMIUM OXIDE ON A SUPPORT COMPONENT SELECTED FROMTHE GROUP CONSISTING OF SILICA, ALUMINA, ZIRCONIA, AND THORIA, HEATINGTHE RESULTING COMPOSITE AT AN ELEVATED TEMPERATURE, UNDER SUBSTANTIALLYANHYDROUS CONDITIONS, AND FOR A SUFFICIENT TIME TO IMPART, TO THERESULTING MIXTURE, INCREASED CATALYTIC ACTIVITY FOR PROMOTING THEFORMATION OF NORMALLY SOLID POLYMERS OF OLEFINS, THE RESULTING CATALYSTCONTAINING AT LEAST PART OF THE CHROMIUM IN THE HEXAVALENT STATE.